Age 18-60 years (inclusive) at the time of signing Informed Consent Form

Diagnosis of progressive MS according to the revised McDonald 2017 criteria, and:

Expanded disability status scale (EDSS) score at screening, from 3 to 6 inclusive Evidence of disability progression and no relapses in the 2 years prior to screening

• Diagnosis of relapsing MS according to the revised McDonald 2017 criteria, and: Evidence of clinical relapses and MRI activity within two years prior to screening while on a disease modifying therapy

EDSS score at screening, from 0 to 6 inclusive

No relapses within 45 days of screening

Pregnant or breastfeeding, or intention of becoming pregnant within the timeframe in which contraception is required

Participants who have confirmed or suspected Progressive Multifocal Leukoencephalopathy (PML)

Known or suspected history of Hemophagocytic Lymphohistiocytosis/ Macrophage Activation Syndrome (HLH/MAS) or neurotoxicity with prior therapies

Known presence of other neurologic disorders that may mimic MS

History of currently active primary or secondary (non-drug-related) immunodeficiency

Significant or uncontrolled medical disease which would preclude patient participation

High risk for clinically significant bleeding or any condition requiring plasmapheresis, IV Ig, or acute blood product transfusions

History of recurrent serious infections or chronic infection

Prior treatment with CAR T-cell therapy, gene-therapy product, total body irradiation, bone marrow transplantation, allograft organ transplant, or hematopoietic stem cell transplant at any point

Any previous treatment with immunomodulatory or immunosuppressive medication without an appropriate washout period.

Inability to complete an MRI scan